The present invention relates to a method for accurately calculating numerical values for a bead shape in arc welding.
Arc welding is a junction technique wherein a plurality of independent welding workpieces are partially melted by high-temperature heat generated by arc discharge and the molten metal solidifies, thereby joining the welding workpieces. This arc welding is broadly divided into two methods: a non-consumable electrode-type arc welding method wherein an arc is generated by a non-consumable electrode and a bead is formed only of molten metal of welding workpieces, and a consumable electrode-type arc welding method wherein filler metal made of a material of the same type as that of welding workpieces and the welding workpieces are melted by arc heat, and the molten filler metal and melted welding workpieces are mixed, thereby forming a bead shape.
Welding quality resulting from this arc welding depends on various factors (welding conditions) including the material of welding workpieces, the shape of a joint, the material of filling metal, components of shielding gas for shielding an arc and a welded part from the atmospheric air, the board thickness of welding workpieces, the welding position, welding current, welding voltage, and welding speed, therefore, priorly, it has been possible for only skilled workers who have acquired experience over a long period of time to set the above welding conditions.
For the purpose of solving this problem, Japanese Unexamined Patent Publication No. Hei-7-214317 and Japanese Unexamined Patent Publication No. Hei-6-214317 have been provided. In Japanese Unexamined Patent Publication No. Hei-7-214317, the shape of a weld bead is made approximate to the area of a half ellipse. In addition, in Japanese Unexamined Patent Publication No. Hei-6-126453, the shape of a bead in a case of fillet welding is calculated in accordance with [Numerical formula 1].
[Numerical formula 1].                                           ⅆ            x                                ⅆ            y                          =                ⁢                              f            ⁡                          (              y              )                                                          1              -                                                f                  2                                ⁡                                  (                  y                  )                                                                                                      f          ⁡                      (            y            )                          =                ⁢                                                            ρ                ⁢                                  xe2x80x83                                ⁢                g                                            2                ⁢                σ                                      ⁢                          y              2                                -                                    1                              R                0                                      ⁢            y                    -                      sin            ⁢                          xe2x80x83                        ⁢            α                              
Herein, xcfx81 represents density of molten metal, g represents acceleration of gravity, "sgr" REPRESENTS surface tension of molten metal, and x, y, a, and R0 represent, in terms of coordinate axes x and y, an angle a between the tangent line of a bead shape and a curvature R0 of the y-axis.
However, with the prior method for setting welding conditions by a skilled worker, it had been necessary even for a skilled worker, in order to set welding conditions to secure the welding quality demanded, to repeatedly make adjustments by use of multiple test materials until appropriate conditions could be obtained in advance, moreover, it had been impossible to infer what the shape of a weld bead after welding would be like.
There have been no means for confirmation of this weld bead shape but to judge, by cutting a welded part of welding workpieces, sufficiently polishing the sectional welded part, and performing etching with a corrosive liquid, as to whether appropriate welding results have been obtained.
In addition, with the method of Japanese Unexamined Patent Publication No. Hei-7-214317, wherein a bead shape is made approximate to the area of a half ellipse, an accurate bead shape cannot be obtained, and particularly, in a case of fillet welding as shown in FIG. 1, a bead shape cannot be made approximate to the area of a half ellipse, therefore, a problem has existed such that a highly accurate weld bead shape cannot be obtained by calculation, and in Japanese Unexamined Patent Publication No. Hei-6-126453, calculation is performed in accordance with [Numerical formula 1], therefore, a problem has existed such that it is possible to determine a shape as shown in FIG. 2, but it is impossible to calculate, by the above numerical formula, a shape as shown in FIG. 3, which occurs in a case where a non-consumable electrode-type arc welding is performed and produces a recess or a shape as shown in FIG. 4, which produces undercuts on the flange side and web side. As the reasons thereof, when [Numerical formula 1] is used, an x-coordinate of a bead shape with respect to an y-coordinate is determined based on a certain initial value (x0, y0), therefore, for expressing the recess on the flange side of FIG. 3 and the undercut on the flange side of FIG. 4, multiple solutions occur, thus a unique solution cannot be determined by a numerical value calculation.
Therefore, it is an object of the present invention to provide, by solving the problem of multiple solutions when the shape causing a recess or undercut on the flange side is determined by calculation, a method for calculating the shape of a bead of a welded part which can easily represent a recess or undercut on the flange side to set an appropriate welding condition.
In order to achieve the above theme, a first aspect of the present invention is a method for calculating the shape of a bead of a welded part in arc welding comprising the steps of:
setting geometric data on the object to be welded, characteristic parameters of the object and welding environment, and welding conditions,
inferring, under the welding conditions, the melting part of the object by a heat conduction calculation,
rotating the coordinates about an axis parallel to the direction of the welding and/or about an axis perpendicular to the welding direction for the calculated melting part,
setting a difference lattice for the coordinate-rotated melting part,
calculating displacement of the melting part, for which the difference lattice is set, by a curved surface equation,
rotating the welding shape determined by the calculated displacement by the same angle of rotation as that of the coordinate rotation in the opposite direction to the rotation direction, and
repeatedly calculating the inference of the melting part by the heat conduction calculation of the displacement shape, the coordinate rotation, the setting of the difference lattice, and the calculation of the displacement of the melting part until a calculation end criterion is met.
A second aspect of the present invention is a method for calculating the shape of a bead of a welded part in arc welding comprising the steps of:
setting geometric data on the object to be welded, characteristic parameters of the object and welding environment, and welding conditions,
rotating the coordinates about an axis parallel to the direction of the welding of the object and/or about an axis perpendicular to the weld line direction,
inferring, based on preset welding conditions, the melting part of the object by a heat conduction calculation,
setting a difference lattice for the melting part,
calculating displacement of the melting part, for which the difference lattice is set, by a curved surface equation,
repeatedly calculating the inference of the melting part by the heat conduction calculation of the displacement shape, the setting of the difference lattice, and the calculation of the displacement of the melting part until a calculation end criterion is met, and
rotating the shape of the invariable melting part and displacement shape by the same angle of rotation as that of the coordinate rotation in the opposite direction to the rotation direction.
A third aspect of the present invention is a method for calculating the shape of a bead of a welded part in arc welding comprising the steps of:
setting geometric data on the object to be welded, characteristic parameters of the object and welding environment, and welding conditions,
inferring, under the welding conditions, the melting part of the object by a heat conduction calculation,
rotating the coordinates about an axis parallel to the direction of the welding and/or about an axis perpendicular to the welding direction for the calculated melting part,
setting a difference lattice for the coordinate-rotated melting part,
adding deposit metal by an amount determined based on the welding conditions to the melting part for which the difference lattice is set,
calculating the displacement of the deposit metal by a curved surface equation,
rotating the welding shape determined by the calculated displacement by the same angle of rotation as that of the coordinate rotation in the opposite direction to the rotation direction, and
repeatedly calculating the inference of the melting part by the heat conduction calculation of the displacement shape, the coordinate rotation, the setting of the difference lattice, the addition of the deposit metal, and the calculation of the displacement of the deposit metal until a calculation end criterion is met.
A fourth aspect of the present invention is a method for calculating the shape of a bead of a welded part in arc welding comprising the steps of:
setting geometric data on the object to be welded, characteristic parameters of the object and welding environment, and welding conditions,
rotating the coordinates about an axis parallel to the direction of the welding of the object and/or about an axis perpendicular to the weld line direction,
inferring, based on preset welding conditions, the melting part of the object by a heat conduction calculation,
setting a difference lattice for the melting part, adding deposit metal by an amount determined based on the welding conditions,
calculating the displacement of the deposit metal, for which the difference lattice is set, by a curved surface equation,
repeatedly calculating the inference of the melting part by the heat conduction calculation of the displacement shape, the setting of the difference lattice, the addition of the deposit metal amount and the calculation of the displacement of the melting part until a calculation end criterion is met, and
rotating the shape of the invariable melting part and displacement shape by the same angle of rotation as that of the coordinate rotation in the opposite direction to the rotation direction.
In addition, in the above first through fourth aspects of the present invention, heat conduction calculation is calculated by a finite difference method or an analytic solution, or by preference from these methods.
Moreover, a calculation is carried out by using a finite difference method as a solution of a curved surface equation.
Furthermore, the calculation end criterion is that the shape of the melting part and/or the displacement shape does not vary or is within an allowable error, or the calculation end criterion is the number of calculations of the shape of the melting part and/or the displacement shape.